Effect on Current Differential Protection Caused by Current Transformer Transient Performance

摘要

Correct action of relay depends largely on the accuracy of current transformer (TA) measuring when the power system is failure. The paper gives a practical current transformer model based on EMTP, and selects actual magnetization current curve and the secondary load. In addition, power system fault is simulated to analyze the effect on differential protection caused by current transformer transient performance. The simulation results shows that: Using actual current transformer of Xibaipo power plant, the unbalanced current generated by the inconsistency of current transformer will not cause differential protection malfunction in high-voltage transmission system; and it can be inferred that we should increase current transformer ratio or capacity to avoid current transformer saturation in low-voltage transmission system.